Metallic silver and copper (II) nitrate and are formed when metallic copper and silver nitrate are reacted . If 3.00 moles of copper metal are reacted how many moles of silver metal will it produced ?

Cu + 2AgNO3 = 2Ag + Cu(NO3)2
Do you see the factors in front of the terms in the equation? These are important because they are the consequence of mass conservation and because you need them for calculations. You see form the equation that from ONE molecule of copper TWO molecules of silver are produced. Moles are the measure of the numbers of molecules (not masses, not volumes, but NUMBERS). For example, one mole is the number of molecules equal to 6x10^23. So, according to the equation you get twice as many silver molecules from each copper molecule -> meaning twice as many moles of silver.